kayak building, Guillemot Fast Double

I finished the basic striping of the hull and deck today, here you can see the double alongside my Petrel

The aft deck before cutting out the cockpit recess

And after cutting out the recess

Now I need a bit of help from kayak builders.
 I want to lower the back of the cockpit in order to make layback rolling easier. This will necessitate lowering the back deck a bit,
 any suggestions?